Porosity dependence of electron percolation in nanoporous Ti O2 layers

Ashi Ofir, Snir Dor, Larisa Grinis, Arie Zaban, Thomas Dittrich, Juan Bisquert

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Abstract

The electron diffusion coefficient at varying porosity has been determined in a series of nanostructured Ti O2 films of different initial thicknesses. The porosity was changed by applying different pressures prior to sintering, thereby modifying the internal morphology of the films though not their chemical and surface conditions. A systematic increase of the effective diffusion coefficient was observed as the porosity was decreased, indicating the improvement of the internal connectivity of the network of nanoparticles. The experimental results have been rationalized using percolation theory. First of all, applying a power law dependence, the diffusion coefficient as a function of porosity from different films collapsed in a single master curve. In addition, application of the models of effective medium approximation (EMA) allows us to compare the experimental results with previous data from Monte Carlo simulation. The different data show a similar dependence in agreement with the EMA predictions, indicating that the geometrical effect of electron transport due to variation of porous morphology in Ti O2 nanoparticulate networks is well described by the percolation concept.

Original languageEnglish
Article number064703
JournalJournal of Chemical Physics
Volume128
Issue number6
DOIs
StatePublished - 14 Feb 2008

Bibliographical note

Funding Information:
The work was supported by Ministerio de Educación y Ciencia of Spain under Project Nos. MAT2007-62982 and HOPE CSD2007-00007 (Consolider-Ingenio 2010) (J.B.) and the Israeli Ministry of Science (the BIU group).

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